With an increase in the amount of information to be processed, there is an increasing demand for preparation or maintenance of communication infrastructure in order to conduct information communication smoothly.
In response to such a demand, in recent years, a communication network by wavelength division multiplex (Wavelength Division Multiplex, hereinafter referred to as “WDM”) (Wavelength Division Multiplex Network, hereinafter referred to as “WDM network”) which is suited to a large volume communication has come to be widespread.
In many cases, the WDM network plays a role as a network backbone such as a marine cable connecting continents. Therefore, if a fault occurs in the WDM network, effects brought by such fault are significantly extensive and serious.
In order to maintain the reliability of a WDM apparatus or a cable constituting the WDM network, maintenance and operation of the apparatus or the cable is of crucial importance.
In the WDM network, the so-called network management system (Network Management System, hereinafter referred to as “NMS”) is incorporated for alarm monitoring or fault recovery, whereby extraction, analysis or the like of alarm information through a dedicated information processing terminal (hereinafter referred to as an “NMS terminal”) become possible.
In addition, an NMS is provided with a data base of connection information relating to path setting (a wavelength and data relating to a destination node), and path setting or path changing can be performed unitarily by a remote operation from an NMS terminal.
As mentioned above, an NMS is a system which is indispensable for enhancing the reliability and convenience of the WDM network. Therefore, the operation of the WDM network largely depends on NMS, and the following troubles may occur.
FIG. 8 is a network configuration diagram showing an example of an end-to-end path composed of a single optical path in a WDM network having an NMS.
FIG. 9 is a data table showing the path connection information of the end-to-end path shown in FIG. 8.
As shown in these figures, a path with a route of a node apparatus 10h→node apparatus 10i→node apparatus 10j is assumed to be set based on a light path of a single wavelength of λ5.
Here, the path setting data of the NMS is assumed to have been disappeared because of an illegal access or the like, and the path which has been set in each node apparatus is assumed to have extinguished.
In this case, an NMS terminal 20, after system initialization, makes an access to the node apparatus 10h and can recognize an output having a wavelength λ5. The NMS terminal 20 can recognize that a WDM signal with a wavelength of λ5 is outputted to the node apparatus 10i. 
Subsequently, the NMS terminal 20 can recognize an output having a wavelength λ5 in the node apparatus 10i. The NMS terminal 20 can recognize that a WDM signal with a wavelength of λ5 is outputted to the node apparatus 10j. 
The NMS terminal 20 can recognize that the node apparatus 10j is the end point of the path, since it cannot recognize the output with a wavelength λ5 in the node apparatus 10j. 
From the above, it can be understood that the NMS terminal 20 can generate path setting data with a single wavelength (λ5) with the node apparatus 10h as the starting point, via the node apparatus 10i, and the node apparatus 10j as the end point. In this way, the original end-to-end path can be restored.
Next, an explanation will be made on a WDM network formed of a plurality of light paths with reference to FIG. 10 and FIG. 11.
FIG. 10 is a network configuration diagram showing an example of an end-to-end path network composed of a plurality of light paths in a WDM network having an NMS.
FIG. 11 is a data table showing the path connection information of the end-to-end path shown in FIG. 10.
Specifically, as shown in FIG. 11, for example, a series of optical transmission path is assumed to be set by a light path between a node apparatus 10k and a node apparatus 10l (wavelength: λ6), wavelength conversion in a node apparatus 10m and a light path (wavelength: λ7) between a node apparatus 10m and a node apparatus 10n. 
Here, the path setting data of the NMS is assumed to have been disappeared as in the case mentioned above, and the path which has been set in each node apparatus is assumed to have extinguished.
In this case, the NMS terminal 20, after system initialization, makes an access to a node apparatus 10k and can recognize an output with a wavelength λ6. The NMS terminal 20 can recognize that a WDM signal with a wavelength of λ6 is outputted to the node apparatus 10l. 
The NMS terminal 20 may erroneously recognize that the node apparatus 10l is the end point of the path, since it cannot recognize an output with a wavelength λ6 in the node apparatus 10l. 
That is, while the original path can be restored in the case where the path is set with a single light path as shown in FIG. 8 and FIG. 9, the original path cannot be restored easily when the path setting data of an NMS disappears in the case where a path is set by a plurality of light paths.
That is, according to the configuration of a path constituting the WDM network, a large amount of time is required for restoring the network, thereby causing extensive and enormous damage or influence.
Patent Document 1 discloses a wavelength path communication network in which each node apparatus calculates and sets a wavelength path based on the use situation of a link connected to its own node as well as on the use situation of a link observed in other nodes.
Patent Document 2 discloses an optical wavelength path setting method in which a sending node sends a receiving node one or more recommended wavelength path information based on the resource use conditions of the receiving node and a relay node, and subsequently, the receiving node selects available recommended wavelength path, sets a resource used in the recommended wavelength path in own node, sends a selected path notification to the relay node and the sending node, and in the sending node and the relay node, sets a resource relating to the received selected path notification in self node.
That is, Patent Documents 1 and 2 propose a technology in which each node sets a wavelength path without using an NMS.    Patent Document 1: JP-A-2003-235061    Patent Document 2: JP-A-2003-234771